Riverine Organic Matter Composition as a Function of Land Use Changes, Southwest Amazon

Bernardes, Marcelo; Martinelli, Luiz Antônio; Krusche, Alex V.; Gudeman, Jack; Moreira, Marcelo Zacharias; Victória, Reynaldo Luiz; Ometto, Jean Pierre Henry Balbaud; Ballester, Maria Victória Ramos; Aufdenkampe, Anthony K.; Richey, Jeffrey E.; Hedges, John I.

doi:10.1890/01-6028

Cited by 69 publications

(37 citation statements)

References 37 publications

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“…C : N ratios of phytoplankton, soil, and leaves range between 5-8, 10-27, and 21-106, respectively (Hedges et al 1986;Trumbore 1993;Devol and Hedges 2001). The d 13 C of C 3 plants range from 226% to 231%, whereas C 4 grasses found on floodplains and in pastures are more enriched (212% to 216% [Hedges et al 1986;Bernardes et al 2004;Mayorga et al 2005a]). The d 13 C of phytoplankton range from 230% to 245% in rivers and lakes (Araujo-Lima et al 1986;Hedges et al 1986;Mayorga et al 2005a).…”

Section: Resultsmentioning

confidence: 99%

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Factors controlling water‐column respiration in rivers of the central and southwestern Amazon Basin

Ellis

Richey

Aufdenkampe

et al. 2012

Limnology & Oceanography

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We examined the factors controlling the variability in water-column respiration rates in Amazonian rivers. Our objectives were to determine the relationship between respiration rates and the in situ concentrations of the size classes of organic carbon (OC), and the biological source (C 3 and C 4 plants and phytoplankton) of organic matter (OM) supporting respiration. Rates were likely elevated in the former rivers, which were all sampled during low water, due to the stimulation of heterotrophic respiration via the supply of a labile, algal-derived substrate and/or the occurrence of autotrophic respiration. The organic composition of fine particulate OM (FPOM) of these rivers is consistent with a phytoplankton origin. Multiple linear regression analysis indicates that [FPOC], C : N FPOC ratios, and [O 2 ] account for a high amount of the variability in respiration rates (r 2 5 0.80). Accordingly, FPOC derived from algal sources is associated with elevated respiration rates. The d 13 C of respiration-derived CO 2 indicates that the role of phytoplankton, C 3 plants, and C 4 grasses in supporting respiration is temporally and spatially variable. Future scaling work is needed to evaluate the significance of phytoplankton production to basin-wide carbon cycling.

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Section: Resultsmentioning

confidence: 99%

“…The d 13 C of phytoplankton range from 230% to 245% in rivers and lakes (Araujo-Lima et al 1986;Hedges et al 1986;Mayorga et al 2005a). The d 13 C of soil generally spans the range of the vegetation types (Bernardes et al 2004). …”

Section: Resultsmentioning

confidence: 99%

Factors controlling water‐column respiration in rivers of the central and southwestern Amazon Basin

Ellis

Richey

Aufdenkampe

et al. 2012

Limnology & Oceanography

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“…Boschker et al (1995) apply such methodologies in Lake Gooimer, and Marchand et al (2005) apply a similar approach to study the sediment in a mangrove system. Relatively comprehensive studies using multiple markers are reported in the Amazon system (Bernardes et al, 2004;Hedges et al, 1994). It must be pointed out that due to the complexity of the composition/source terms of organic matter and the biogeochemical evolvement they undergo in the estuarine environments, such multiple markers are important because each individual marker may be subject to limitations.…”

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Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions

Dai

Huang

et al. 2010

Biogeosciences

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Abstract. Organic matter in surface sediments from the upper reach of the Pearl River Estuary and Lingdingyang Bay, as well as the adjacent northern South China Sea shelf was characterized using a variety of techniques, including elemental (C and N) ratio, bulk stable organic carbon isotopic composition (δ 13 C), and carbohydrate composition analyses. Total organic carbon (TOC) content was 1.21 ± 0.45% in the upper reach, down to 1.00±0.22% in Lingdingyang Bay and to 0.80 ± 0.10% on the inner shelf and 0.58 ± 0.06% on the outer shelf. δ 13 C values ranged from −25.1‰ to −21.3‰ in Lingdingyang Bay and the South China Sea shelf, with a trend of enrichment seawards. The spatial trend in C/N ratios mirrored that of δ 13 C, with a substantial decrease in C/N ratio offshore. Total carbohydrate yields ranged from 22.1 to 26.7 mg (100 mg OC) −1 , and typically followed TOC concentrations in the estuarine and shelf sediments. Total neutral sugars, as detected by the nine major monosaccharides (lyxose, rhamnose, ribose, arabinose, fucose, xylose, galactose, mannose, and glucose), were between 4.0 and 18.6 mg (100 mg OC) −1 in the same sediments, suggesting that significant amounts of carbohydrates were not neutral aldoses. Using a two end-member mixing model based on δ 13 C values and C/N ratios, we estimated that the terrestrial organic carbon contribution to the surface sediment TOC was ca. 78±11% for Lingdingyang Bay, 34±4% for the inner shelf, and 5.5 ± 1% for the outer shelf. The molecular composition of the carbohydrate in the surface sediments also suggested that the inner estuary was rich in terrestrially derived carbohydrates but that their contribution decreased offshore. A relatively high abundance of deoxyhexoses in the estuary and Correspondence to: M. Dai (mdai@xmu.edu.cn) shelf indicated a considerable bacterial source of these carbohydrates, implying that sediment organic matter had undergone extensive degradation and/or transformation during transport. Sediment budget based on calculated regional accumulation rates showed that only ∼50% of the influxes of terrestrial organic carbon were accumulated in the estuary. This relatively low accumulation efficiency of terrestrial organic matter as compared to the total suspended solids (accumulation efficiency ∼73%) suggested significant degradation of the terrestrial organic carbon within the estuarine system after its discharge from the river. This study demonstrated that the combination of the bulk organic matter properties together with the isotopic composition and molecular-level carbohydrate compositions can be an efficient way to track down the source and fate of organic matter in highly dynamic estuarine and coastal systems. The predominance of terrestrially originated organic matter in the sediment and its generally low accumulation efficiency within the estuary is not surprising, and yet it may have important implications in light of the heavy anthropogenic discharges into the Pearl River Estuary during the past thirty years.

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“…The area of each watershed and land cover data were obtained using remote sensing techniques combined with geographic information systems described in Bernardes et al (2004). The only exception to this procedure was the Óbidos sampling site on the Amazon River, where we assumed that the percentage deforested area was the same as for the Brazilian Amazon estimated by Instituto Nacional de Pesquisas Espaciais (INPE).…”

Section: Methodsmentioning

confidence: 99%

Dissolved nitrogen in rivers: comparing pristine and impacted regions of Brazil

et al. 2010

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Riverine nitrogen distribution is increasingly controlled by anthropogenic activities in their watersheds, regardless of spatial scale, climate, and geographical zone. Consequently, modelling efforts to predict the export of nitrogen from rivers worldwide have used attributes such as population density, land use, urbanization and sanitation. These models have greatly enhanced our understanding of the sources and fate of nitrogen added to terrestrial systems and transported to rivers and streams, especially for developed countries of the North temperate zone. However, much of the world's population lives in developing countries of the tropics, where the effects of human activities on riverine N exports are still poorly understood. In an effort to close this gap, we compare riverine nitrogen data from 32 Brazilian rivers draining two contrasting regions in this tropical country in terms of economic development -the State of São Paulo and the Amazon. Our data include nitrogen in different dissolved forms, such as Dissolved Inorganic Nitrogen (DIN) and Dissolved Organic Nitrogen (DON). The results show that nitrogen concentrations decreased as river runoff increased in both study areas, and that concentrations were significantly higher in rivers draining the most economically developed region. The relationships between nitrogen concentrations and fluxes with demographic parameters such as population density were also determined and compared to those in temperate systems. In contrast to temperate watersheds, we found that nitrogen fluxes increased only after population densities were higher than 10 individuals per km 2 .Keywords: nitrogen, river, pollution, Piracicaba basin, Amazon basin, Brazil. Nitrogênio dissolvido em rios de regiões distintas do Brasil ResumoA carga do nitrogênio em rios é cada vez mais controlada por atividades humanas independentemente da escala espacial, do clima, ou da região geográfica. Consequentemente, esforços de modelagem que predizem exportação de nitrogênio usam atributos que refletem atividades humanas, tais quais, densidade populacional, uso do solo, urbanização e saneamento ambiental. Estes modelos têm aumentado significativamente nosso entendimento sobre as fontes e destino do nitrogênio adicionado ao sistema terrestre e transportado aos sistemas aquáticos, especialmente em países desenvolvidos localizados no Hemisfério Norte. Entretanto, a maioria da população mundial vive em países em desenvolvimento dos trópicos, onde os efeitos das atividades humanas sobre a carga de nitrogênio nos rios são pobremente entendidos. Em um esforço para aumentar nossa compreensão sobre este fenômeno, comparamos a distribuição de nitrogênio dissolvido em 32 rios brasileiros, drenando duas regiões contrastantes em termos de desenvolvimento econômico -rios do Estado de São Paulo e da região Amazônica. Nossos dados incluem nitrogênio em duas formas dissolvidas: inorgânica (NID) e orgânica (NOD

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Riverine Organic Matter Composition as a Function of Land Use Changes, Southwest Amazon

Cited by 69 publications

References 37 publications

Factors controlling water‐column respiration in rivers of the central and southwestern Amazon Basin

Factors controlling water‐column respiration in rivers of the central and southwestern Amazon Basin

Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions

Dissolved nitrogen in rivers: comparing pristine and impacted regions of Brazil

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